Engee documentation

Washout (Discrete or Continuous)

A washout filter (high-pass filter) in discrete or continuous time.

blockType: SubSystem

washout discrete or continuous

Path in the library:

/Physical Modeling/Electrical/Control/General Control/Washout (Discrete or Continuous)

Description

Block Washout (Discrete or Continuous) implements a washout filter in accordance with IEEE 421.5-2016 [1]. A washout filter is also known as a high-pass filter.

You can switch between continuous and discrete filter implementations using the parameter Sample time (-1 for inherited).

The equations

notable mode

To set the filter for continuous operation, set the parameter Sample time (-1 for inherited) meaning 0. This representation is equivalent to a continuous transfer function.

where — the time constant of the filter.

The above transfer function implies a system of equations defining the filter:

where

  • — filter input signal;

  • — filter status;

  • — filter output signal;

  • — simulation time;

  • — the initial value of the input signal of the block.

discret mode

To set the filter to work in discrete mode, set the parameter Sample time (-1 for inherited) a positive non-zero value or a value −1 to inherit the sampling period from the upstream block. The discrete representation is equivalent to the transfer function

where — the sampling period.

Based on the discrete transfer function, the filter equations are determined using the direct Euler method:

where

  • — filter input signal;

  • — filter status;

  • — filter output signal;

  • — time step of the simulation;

  • — the initial input signal of the block.

Determining the initial conditions

The initial conditions of the block can be set using the parameter Initialization. Set the value:

  • Inherited from block input — the unit will set the initial conditions of the status and output signal equal to the initial input value;

  • Specify as parameter — the block will set the initial condition of the state equal to the value of the parameter Initial state.

Ignoring the filter dynamics

To ignore the filter dynamics, set the time constant value to less than or equal to the value of the sampling period. In this case, the input signal is applied directly to the output:

In continuous mode, the sampling period and the time constant must be zero.

Ports

Input

# u — filter input
vector

Details

The input signal of the filter is washed out. The block uses the initial value of the input signal to determine the initial value of the state.

Data types

Float32, Float64
Complex numbers support

I don’t

Output

# y — filter output signal
vector

Details

The output signal of the filter is washed out.

Data types

Float32, Float64
Complex numbers support

I don’t

Parameters

Main group

# Time constant — filter time constant

Details

The time constant of the washout filter. To ignore the filter dynamics, set this parameter to a value less than or equal to the parameter value. Sample time (-1 for inherited).

Default value

0.1
Program usage name

T
Evaluatable

Yes

# Initialization — the method of setting the initial state
Inherited from block input | Specify as parameter

Details

Select the initial state for this block. For more information, see Determining the initial conditions.

Values

Inherited from block input | Specify as parameter
Default value

Inherited from block input
Program usage name

initial_option
Evaluatable

Yes

# Initial state — initial state

Details

The initial state of the block.

Dependencies

To use this parameter, set for the parameter Initialization meaning Specify as parameter.

Default value

0.0
Program usage name

initial_state
Evaluatable

Yes

# Sample time (-1 for inherited) — block sampling period

Details

The time between consecutive block executions. During execution, the block generates output signals and, if necessary, updates its internal state.

For the inherited discrete time mode, set this parameter to −1. For discrete mode, set this parameter to a positive integer. For continuous mode, set this parameter to 0.

Default value

-1
Program usage name

sample_time
Evaluatable

Yes

Literature

  1. IEEE Recommended Practice for Excitation System Models for Power System Stability Studies. IEEE Std 421.5-2016. Piscataway, NJ: IEEE-SA, 2016.